Portland is the one large American city that comes the closest to adopting a "truly comprehensive" set of policies to promote bicycling as a mainstream transportation choice, according to a new report for the U.S. Department of Transportation.

John Pucher and Ralph Buehler, the two most prominent bicycling researchers in the country, studied nine large cities in the U.S. and Canada that have promoted cycling and singled out Portland for their highest praise.

"Portland's success is evident in the numbers, with a 6-fold increase in cycling levels since 1990," Pucher and Buehler concluded.

Their study shows, they say, that bike lanes and off-street paths play an important role in increasing bicycle use. But they say that very large cities in the study that have done a lot to promote cycling, such as New York and Chicago, find it more difficult to increase their cycling rates, in part because of the "sometimes harrowing experience of cycling in heavy traffic with high levels of noise and air pollution."

Overall, among the nine cities, Portland has the highest share of commuters -- 5.8 percent -- who cycle to work. Minneapolis is second with 3.9 percent and Vancouver, B.C., is third with 3.7 percent. The three are the smallest of the nine cities and have the safest cycling, Pucher and Buehler report.

Among the 100 largest U.S. cities, Portland also has the highest share of bike commuters, according to the report. And it is second only to New York City in the total number of average daily bike commuters. New York City had 24,000 daily bike commuters, compared to 13,200 for Portland. Chicago and Los Angeles are next in line with each having fewer than 13,000 daily bike commuters.

The report is intended to demonstrate how cities can encourage cycling, and the researchers praise Portland for its wide variety of pro-cycling policies. Of primary importance is the city's dense bikeway network, which includes bike lanes, low-traffic bike boulevards and off-street paths. In addition, the city led the way in installing on-street bicycle parking corrals, has a large number of cycling events and a "lively bike culture."

"The success of Portland is important because it shows that even car-dependent American cities can greatly increase cycling by implementing the right package of infrastructure, programs, and policies," the report concludes.